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electrical:12v:alternator [2019/06/03 17:07]
frater_secessus [when alternator charging works well] |
electrical:12v:alternator [2019/10/01 12:33]
frater_secessus [limitations] |
| ===== limitations ===== | ===== limitations ===== |
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| Alternator charging is generally only practical for the [[electrical:12v:charging|bulk charge stage]] due to relatively low voltage output and the [[electrical:12v:charging|long time periods required for absorption]]. It is unlikely to get the house battery completely charged unless one is driving significant distances. This can have an impact on battery longevity. If one drives often [[electrical:12v:alt_and_solar|a combination of the alternator doing bulk charging and a small solar doing the rest]] is good match. | Alternator charging is generally only practical for the [[electrical:12v:charging|bulk charge stage]] due to relatively low voltage output and the [[electrical:12v:charging|long time periods required for absorption]]. It is unlikely to get the house battery completely charged unless one is driving significant distances. This can have an impact on [[electrical:batterycide|battery longevity]]. If one drives often [[electrical:12v:alt_and_solar|a combination of the alternator doing bulk charging and a small solar doing the rest]] is good match. |
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| | See [[electrical:12v:mandatory solar|Is Solar Mandatory?]] for ideas on how to charge primarly by alternator. |
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| | ===== effect on alternator ===== |
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| | Charging the house batteries from the alternator increases the load on the alternator and can be expected to contribute to somewhat earlier failure. The shortened life may be trivial if alternator charging is done thoughtfully, and may be sudden if done without considering the effects of higher alternator loading. |
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| | SternWake reports **idling while charging causes a sharp increase in alternator temperature**.((http://www.cheaprvliving.com/forums/Thread-Longer-alternator-life-when-used-to-charge-house-batteries?pid=182096#pid182096)) To avoid this, do your alternator charging while driving. This will ensure airflow over the hot alternator. |
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| | Lithium in particular has low internal resistance and can pull [[electrical:12v:battery_capacity|1C]] (100A for an 100Ah bank) or more. Most AGM will pull about C/3 (33A for a 100Ah bank) but premium brands may do more. Flooded lead-acid batteries tend to pull less current (C/5, 20A per 100Ah of bank). Victron posted [[https://www.youtube.com/watch?v=jgoIocPgOuga video]] showing it is possible to "smoke" an alternator while charging lithium. |
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| | Since lithium does not care much about [[electrical:depth_of_discharge|state of charge]], there is little reason to go for maximum force charging. Some Li bank owners use [[electrical:12v:b2b|DC-DC isolators]] which limit themselves to a particular output (20A, 60A, 100A, etc).((https://shop.pkys.com/Alternator-Lithium-Battery.html)) |
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| | Reasonable charging rates can also be easier on the alternator when charging suddenly stops, whether by completion((same reason headlights are turned on at the donor car when jumpstarting)) or BMS intervention. |
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| | Blue Sea makes an [[https://www.bluesea.com/resources/91|alternator field disconnect]] which shuts down alternator power just before disconnecting the load, but this may be chiefly applicable to marine alternators. Others have discussed installing a small lead-acid battery parallel to the Li bank; in theory this could soften the blow from Li leaving the circuit. Other sources suggest the presence of the starter battery would be sufficient.((https://shop.pkys.com/Alternator-Lithium-Battery.html)) |
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| Charging the house batteries from the alternator increases the load on the alternator and can be expected to contribute to earlier failure. SternWake reports **idling while charging causes a sharp increase in alternator temperature**.((http://www.cheaprvliving.com/forums/Thread-Longer-alternator-life-when-used-to-charge-house-batteries?pid=182096#pid182096)) So don't idle it! | |
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| Also see [[electrical:12v:mandatory solar|Is Solar Mandatory?]] for ideas on how to charge primarly by alternator. | |
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| ===== isolators ===== | ===== isolators ===== |
| - [[http://amzn.to/2gVwmKw|solid state isolator]] - an electronic device which uses diodes to prevent depletion of the starter battery. **Isolators are generally brick-shaped**. Diode-based isolators have a **0.5v - 1v drop** between the alternator and house battery. This may be desirable if the house battery is a lower-voltage chemistry like [[electrical:12v:lifepo4_batteries_thread|LiFePO4]]. Some solid state isolaters use FETs and diodes in tandem to reduce voltage drop. \\ Note: solid state relays can't combine batteries for self-jumpstarting. | - [[http://amzn.to/2gVwmKw|solid state isolator]] - an electronic device which uses diodes to prevent depletion of the starter battery. **Isolators are generally brick-shaped**. Diode-based isolators have a **0.5v - 1v drop** between the alternator and house battery. This may be desirable if the house battery is a lower-voltage chemistry like [[electrical:12v:lifepo4_batteries_thread|LiFePO4]]. Some solid state isolaters use FETs and diodes in tandem to reduce voltage drop. \\ Note: solid state relays can't combine batteries for self-jumpstarting. |
| - manual switch - A [[http://amzn.to/2gsDtNc|manual battery switch]] normally has 4 positions: A, B, A+B, and Off. A would be for the starter battery and used during starting. B would be used for house use when one is not driving. A+B could be used to combine both sets for starting or for charging while driving. This kind of setup is prone to user error. A manual switch has no current or voltage losses. | - manual switch - A [[http://amzn.to/2gsDtNc|manual battery switch]] normally has 4 positions: A, B, A+B, and Off. A would be for the starter battery and used during starting. B would be used for house use when one is not driving. A+B could be used to combine both sets for starting or for charging while driving. This kind of setup is prone to user error. A manual switch has no current or voltage losses. |
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| | ===== sizing an isolator ===== |
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| | If an isolator is **oversized** it will cost more for no benefit and will self-consume somewhat more energy to hold the combining circuit closed.((an electromagnet holds the parts of the active circuit together. When power to the inolator input is cut the electromagnet can no longer hold the circuit closed. The circuit is open and the batteries are isolated from each other.)) \\ |
| | If an isolator is **undersized** (less common) it will not be able to carry enough current, resulting in overheating and/or [[electrical:12v:alternator#sudden_disconnection|sudden shutdown]]. |
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| | ==== flooded lead-acid ==== |
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| | FLA batteries can accept up to [[electrical:12v:battery_capacity|C]]/5 in [[electrical:12v:charging|Bulk stage]]. |
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| | Example: a 200Ah FLA battery bank will pull up to 40A((200Ah/5)) in Bulk charging. An isolator rated for constant duty at 40A((likely with peak tolerance of 60A or so)) would be sufficient.((assuming you aren't applying heavy loads like a microwave while driving)) |
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| | ==== AGM lead-acid ==== |
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| | Consumer-grade AGM batteries typically will accept C/5 - C/3. |
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| | Example: a 200Ah AGM bank will pull up to 67A in Bulk. A 75A isolator((100A peak)) would be sufficient. |
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| | Note: high-end AGM like Lifeline, Odyssey, Rolls, etc, can pull massive current when charging. 200A+ would be possible for the example bank and could shorten the life of a stock alternator. |
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| | ==== lithium ==== |
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| | Lithium also has the ability to accept massive amounts of charging. It will do so across the entire charging range, as lithium does not have an Absorption phase the way lead-acid does. |
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| | Example: 200Ah of lithium could easily accept 200Ah+. There are mitigating factors, however. |
| | * Because lithium can use about 80% of it's capacity instead of 50% for lead-acid, 120Ah of lithium is a common replacement for 200Ah lead-acid banks. So the lithium bank would "only" draw 120A instead of 200A. |
| | * drop-in lithium banks like [[https://amzn.to/2J10vpZ|Battleborn]] have a battery monitoring system (bms) to shut down charging if current exceeds specs. |
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| | ==== sudden disconnection ==== |
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| | **Sudden disconnection of a large load((including a charging battery)) when the alternator is running** can damage the alternator and any operating chassis electronics. Sudden disconnection can occur when: |
| | * an isolator shuts off due to current beyond it's rating |
| | * a BMS shuts off lithium charging. This can include overvoltage, overcurrent, temperature extremes, etc. |
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| ===== gotchas ===== | ===== gotchas ===== |
| * a higher-output alternator will put out more power | * a higher-output alternator will put out more power |
| * a different **voltage regulator** for older vehicles, [[http://www.cheaprvliving.com/forums/Thread-Your-Vehicles-voltage-regulator|as demonstrated by SternWake]], increases the voltage available for charging but also increases the coach voltage. | * a different **voltage regulator** for older vehicles, [[http://www.cheaprvliving.com/forums/Thread-Your-Vehicles-voltage-regulator|as demonstrated by SternWake]], increases the voltage available for charging but also increases the coach voltage. |
| * a [[http://www.sterling-power-usa.com|Sterling]] "fake load" regulator will cause the alternator to put out more amps and then will DC-DC convert the voltage up to correct charging range.((http://www.sterling-power-usa.com/library/What%20is%20an%20alternator%20to%20battery%20charger.pdf)). This is the opposite direction of how [[electrical:solar:charge_controller|MPPT charging]] works. | * a [[http://www.sterling-power-usa.com|Sterling]] "fake load" regulator will cause the alternator to put out more amps and then will DC-DC convert the voltage up to correct charging range.((http://www.sterling-power-usa.com/library/What%20is%20an%20alternator%20to%20battery%20charger.pdf)). This is the opposite direction of how [[electrical:solar:charge_controller|MPPT charging]] works. Also see [[electrical:12v:b2b|b2b chargers]]. |
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| ===== using the coach battery only ===== | ===== using the coach battery only ===== |
| A simple possible approach would be to replace the starter battery with a marine or AGM battery.((http://www.cheaprvliving.com/forums/Thread-Easiest-simplest-cheapest-power-set-up)) | A simple possible approach would be to [[electrical:solar:shallow_cycling|replace the starter battery with a marine or AGM battery]].((http://www.cheaprvliving.com/forums/Thread-Easiest-simplest-cheapest-power-set-up)) |
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| ===== further reading ===== | ===== further reading ===== |
